Foams formed by hardening emulsions of glycol in polyester resin

ABSTRACT

Polyester foams are formed by emulsifying a mixture of glycol in polyester and vinyl monomer and hardening the polyester resin. The resulting polyester resin foam is dimensionally stable, inexpensive to produce, and may be used as furniture, building material and ornamental objects.

United States Patent Parker et al.

[ June 27, 1972 FOAMS FORMED BY HARDENING EMULSlONS OF GLYCOL lN POLYESTER RESIN Earl E. Parker, Allison Park; Charles B. Friedlander, Pittsburgh, both of Pa.

PPG Industries, lnc., Pittsburgh, Pa.

Dec. 2, 1969 Inventors:

Assignee:

Filed:

Appl. No.:

US. Cl ..260/2.5 N, 260/22 D, 260/29.6 NR,

260/33.4 R, 260/861 Int. Cl. ..C08j 1/14 Field of Search ..260/2.5 N, 2.5 B, 33.4 R, 228

Primary Examiner-Samuel H. Blech Assistant ExaminerMorton Foelak Attorney-Chisholm and Spencer [57] ABSTRACT Polyester foams are formed by emulsifying a mixture of glycol in polyester and vinyl monomer and hardening the polyester resin. The resulting polyester resin foam is dimensionally stable, inexpensive to produce, and may be used as furniture, building material and ornamental objects.

8 Claims, No Drawings FOAMS FORMED BY HARDENING EMULSIONS F GLYCOL IN POLYESTER RESIN Molded polyester resins are used extensively as building materials, ornamental objects, furniture, and for many other uses where a strong, inexpensive, shaped object is desired. The polyester resin moldings are formed by polymerizing unsaturated polyesters with ethylenically unsaturated monomers and curing the polyester resin in a shaped mold. The resulting polyester resin assumes the shape of the mold and is cured so that it is hard.

In order to make the molded objects inexpensively, it has been proposed to add water to the unsaturated polyesters and ethylenically unsaturated monomers and subsequently form a water in polyester-vinyl monomer emulsion and then cure the polyester resin in a mold. in this manner, the hardened emulsion mold contains the separate waterdroplets as .the discontinuous phase and the polyester resin as the continuous phase. Thus, when the polyester resin phase in hardened, the resulting material is a foam containing a closed cell polyester resin matrix having a plurality of interstices of water.

The shaped materials resulting from the use of water in polyester resin emulsions have the disadvantage of losing weight over periods of time and after the passage of a somewhat less than reasonable amount of time develop cracks and numerous other imperfections due to the seeping of water through the hardened emulsion. Hence, their use as furniture and ornamental objects has been somewhat limited as these objects are dimensionally unstable and tend to crack and lose their shape and weight.

It has now been discovered that shaped materials which will not lose weight over a period of time and having comparable strength to that of the shaped materials fonned from water and polyester-vinyl monomer emulsions may be made inexpensively by emulsifying a glycol and a mixture of polyester and vinyl monomer in which the glycol is immiscible and curing the polyester resin phase of the emulsion so that a polyester resin matrix containing interstices of glycol is formed. The resulting molding is extremely crack-resistant.

Thus, shaped, articles may be formed by adding a glycol to a copolymerizable mixture of an ethylenically unsaturated polyester and a copolymerizable ethylenically unsaturated monomer such as styrene. The resulting mixture is then agitated and a lipophilic emulsifier is added to the mixture in order to obtain a stable glycol in polyester resin emulsion. The polyester resin phase of the emulsion which, of course, is the continuous phase or the matrix which contains separate droplets of glycol in its interstices is hardened to form a stifi closed cell material without destroying the dispersed character of the glycol. The material may be hardened in a mold and the hardened foam assumes the shape of the mold.

The continuous phase of the emulsion comprises the polyester-vinyl monomer phase. The polyester resin is formed by copolymerizing the mixture of an ethylenically unsaturated polyester and a polymerizable ethylenically unsaturated monomer copolymerizable with the polyester. The copolymerization or hardening of the polyester resin around the glycol takes place after the glycol in polyester-vinyl monomer emulsion is formed.

The polyesters used herein are unsaturated polyesters prepared by condensing one or more dicarboxylic acids or their anhydrides with one or-more polyols wherein one or more of the dicarboxylic acids is ethylenically unsaturated. The ethylenically unsaturated polycarboxylic acids include such acids as:

maleic acid fumaric acid aconitic acid mesaconic acid citraconic acid itaconic acid and halo and alkyl derivatives of such acids and the like; the preferred acid being maleic acid. The anhydrides of these acids, where the anhydrides exist, are, of course, embraced under the term acid", since the polyesters obtained therefrom are essentially the same whether the acid or anhydride is utilized in the reaction. The ethylenically. unsaturated dicarboxylic acids are conventionally employed in an amount of about 10 mole percent to about 100 mol percent, although preferably in an amount of about 20 mole percent to about mole percent of the total moles of acid component in the polyester.

The polyhydric alcohols useful in preparing unsaturated polyesters include:

ethylene glycol diethylene glycol triethylene glycol polyethylene glycol propylene glycol dipropylene glycol polypropylene glycol glycerol neopentyl glycol pentaerythritol trimethylol propane trimethylol ethane and the like. The preferred polyols for the purposes of this invention have a molecular weight of less than about 2,000 and consist essentially of carbon, hydrogen and oxygen. The polyhydric alcohols are generally employed in an equal molar ratio to the total acid components, or as a slight excess, as, for example, about 5 mole percent excess.

Saturated dicarboxylic acids may be utilized in combination with the unsaturated acid or anhydride in the preparation of unsaturated polyesters. Such acids increase the length of the polyester without adding additional cross-linking sites, which is a desired feature in some polyesters. Examples of useful dicarboxylic acids which are either saturated or only aromatically unsaturated include:

succinic acid adipic acid suberic acid ,azelaic acid sebacic acid phthalic acid isophthalic acid terephthalic acid t'etrachlorophthalic acid hexachloroendomethylenetetrahydrophthalic acid and the like. As in the case of the ethylenically unsaturated acids, the anhydrides of these acids, where the anhydrides exist, are, of course, embraced in the term acid", since the polyesters obtained therefrom are the same. Furthermore, for

purposes of the present invention, the aromatic nuclei of such acids as phthalic acid are generally regarded as saturated since the double bonds do not react by addition, as do ethylenic groups. Therefore, wherever the term saturated dicarboxylic acid" is utilized, it is to be understood that such term includes the aromatically unsaturated dicarboxylic acids. Such saturated carboxylic acids may also be referred to as nonethylenically unsaturated polycarboxylic acids.

The vinyl monomers mixed with the above unsaturated polyesters may be any ethylenically unsaturated monomer which is copolymerizable with the polyester and in which the polyester is soluble and which is capable of forming an emulsion with the glycol and polyester. Examples of such monomers are:

styrene halogenated styrenes vinyl toluene divinyl benzene octyl acrylate octyl methacrylate and the like. The preferred monomers are liquid compounds, soluble in the polyester componentsSuch monomers should preferably be free of non-aromatic carbon-carbon conjugated double bonds.

The monomer component or components may be employed over a broad range, but usually the proportion thereof, upon a weight basis, will be less than the polyester component. The amount of monomer should be sufficient to provide a liquid, fiowable, interpolymerizable mixture. Ordinarily, the percentage of monomer will fall within the range of about percent to about 60 percent by weight of the total mixture of polyester and monomer. At the preferred range, the monomer is present in an amount of about percent to about 50 percent.

The glycol is added to the polyester-vinyl monomer mixture and the emulsion is formed. Any liquid glycol which is immiscible with the polyester resin formed may be used. Examples of the polyhydric alcohols or glycols'which may be used are ethylene glycol, glycerine, propylene glycol, diethylene glycol, and the like. The most preferred glycol is ethylene glycol.

Although it is preferred that the glycol be added alone, it may be added as a solution in other materials wherein the glycol comprises at least about 80 percent by weight of the solution.

The amount of glycol added to the mixture of polyester and vinyl monomer may be up to about 80 percent by weight of the mixture. Preferably, the emulsion contains 50 percent by weight of the polyester-vinyl monomer mixture and 50 percent by weight of the glycol.

The mixture of the polyester and vinyl resin and glycol is formed into an emulsion after the addition of an emulsifier. The emulsifier used must be predominantly lipophilic. In other words, the HLB number (hydrophilic-lipophilic balance) must be low. The preferred HLB number is from 2 to 8. These emulsifiers will affect the formation of glycol in polyester emulsions rather than polyester in glycol emulsions where the glycol phase would be the continuous phase and the polyestervinyl monomer mixture would form the interstices. Examples of lipophilic emulsifiers are nonionic mono-, di, tri-, etc., esters formed between polyhydroxy alcohols and fatty acids, such as sorbitan sesquioleate, sorbitan monostearate, sorbitan monooleate, sorbitan monopalmitate, propylene glycol monolaurate, diethylene glycol monooleate, diethylene glycol monostearate, a polyoxyethylenesorbitol derivative of beeswax, glyceryl monostearate, and mixtures thereof. The amount of emulsifier added is generally from about 0.1 to about 10 percent by weight of the mixture. 1

The emulsion is prepared by adding the emulsifier to the mixture of polyester-vinyl monomer and glycol. The glycol may be added either before or after the addition of the emulsifier. The mixture is then agitated by any means to form the emulsion. No specific temperature control is necessary so long as the mixture remains liquid.

The polyester-vinyl monomer phase of the emulsion is hardened or copolymerized by the addition of a free-radical forming catalyst such as an organic peroxide.

lt will be realized that other radical-fonning compounds such as azonitriles can also be used. Any peroxide that is a liquid or is soluble in the emulsion is suitable for use. Specific examples of such peroxides are methyl ethyl ketone peroxide, benzoyl peroxide, tert-butyl hydroperoxide, isopropyl peroxydicarbonate, dichlorobenzoyl peroxide, acetyl peroxide, cumene hydroperoxide and cyclohexyl hydroperoxide. The compound forming free-radicals is used in a concentration that is required for the rapid initiation of the hardening of the polyester and the vinyl monomer. This concentration varies with the conditions of hardening and with' the nature of the polyester, and is generally between 0.001-l0 weight-percent based on the vinyl monomer.

If the freewadical initiator is added before the emulsion has been formed, the polyester-vinyl monomer mixture may have a tendency to gel prematurely. To guard against such an occurrence, an inhibitor is generally added. Some examples of inhibitors which may be added are:

P-benzoquinone chloranil hydroquinone 3-isopropyl catechol 3-methyl catechol 4-isopropyl catechol trimethylamine hydrochloride N-benzylaniline hydrochloride trimethyl benzyl ammonium acid oxalate trimethyl benzyl ammonium maleate trimethyl benzyl ammonium chloride and the like. The amount of inhibitor used is susceptible to wide variation, but conveniently is in a range of about 0.001 percent to about 0.1 percent by weight based on the polyester component of the mixture. 7

The above-mentioned organic peroxide catalysts decompose very slowly at room temperature; they must be made to decompose for the formation of a free-radical which is to initiate the hardening reaction. Normally, temperatures of 65 C. and higher are required to reach a satisfactory hardening time. The mixture of polyester and vinyl monomer can however be hardened at room temperature if the mixture incorporates a suitable promoter, facilitating the decomposition of the peroxide. The type of promoter used depends on the nature of the organic peroxide employed as a radical-forming catalyst. Tertiary aromatic amines such as dimethylaniline or p-toluidine are very effective promoters for diacyl peroxides such as benzoyl peroxide. Similarly, cobalt salts, such as cobalt naphthenate, are very effective promoters for ketone peroxides such as methyl ethyl ketone peroxide. In the present invention, the addition of a promoter is preferred, because the stability of the emulsion may be lost when the emulsion is heated to the temperature that is required for the hardening in the absence of a promoter. If only a somewhat elevated temperature is required, however, no promoter need be introduced. The amount of promoter generally needed varies between about 0.1 and 5 weight-percent and preferably between about 0.2 and 0.5 weight-percent of the polyestervinyl monomer mixture. The mixtures may be modified by the addition of fillers, pigments, and other materials, if desired.

The emulsions are hardened by setting the emulsions in a mold and adding the free-radical catalyst and, if desired, heating at elevated temperatures. In this way, the polyester resin phase copolymerizes forming a closed cell matrix wherein the glycol droplets are dispersed in the interstices of the polyester resin matrix. The hardened emulsion takes the shape of the mold.

The hardened emulsions maybe used as ornamental ob- ,jects, furniture, wood substitutes, building materials, etc. As

the hardened emulsions will. not lose their shape, they are most useful as furniture, and as the glycol droplets will not escape, forcing the hardened emulsions to crack, ornaments which are extremely economical to form may be produced by the method of this invention.

The following examples set forth specific embodiments of the instant invention; however, the invention is not to be construed as being limited to these embodiments, for there are, of course, numerous possible variations and modifications.

EXAMPLE 1 A hardened unsaturated polyester resin matrix having a plurality of interstices of glycol was formed in the following manner.

A reactor was charged with grams of a polyester composition comprising 50 percent styrene, 0.01 percent methyl hydroquinone and 50 percent of a polyester having the following composition:

Moles Maleic anhydride 8 Dimerized fatty acid forme by dimerizing 2 monobasic acids containing 18 carbon atoms (Empol 1014) 2 Neopentyl glycol 10.9

The polyester were added 2 cubic centimeters of cobalt octoate accelerator, and the mixture was stirred. To the mixture were then added 3 grams of sorbitan sesquioleate. After agitating the mixture, 100 grams of ethylene glycol were The emulsion was poured in a mold and hardened in l minutes.

The resulting casting is hard, crack-resistant, and dimensionally stable.

The emulsion was poured in a mold and hardened in 5 minutes at room temperature. EXAMPLE 4 The resuhmg castmg hard crack'reslsmmi and A hardened unsaturated polyester resin matrix having a plu- Slonany stable: rality of interstices of glycol was formed in the following manner. 10 EXAMPLE 2 Atreactor was charged with t10:) gramsoo 1a polyester cam; post ion comprising percen s yrene, percen me y A hardened unsaturated polyester resin matrix having a pluhydro uinone and 60 er ent of a polyester having the followrality of interstices of glycol was formed in the following ing composition:

manner. i 5

A reactor was charged with lOO grams of a polyester com- Moles position comprising 50 percent styrene, 0.01 percent methyl phlhillic anhydfide 2 hydroquinone and 50 percent of a polyester having-the followanhydnde 8 Dlethylene glycol 10 mg composition:

Moles To the polyester were added 2 cubic centimeters of cobalt oclsophthalic acid 6 toate accelerator, and the mixture was stirred. To the mixture Maleic flnhydfilk 4 were then added 3 rams of sorbitan ses uioleate. After Propylene glycol ll.5 a g gitatmg the mixture, 100 grams of .glycenne were added. After further agitation, 0.5 cubic centimeter of To the poayester g cublc i z a dimethylaniline and 0.5 gram of methyl ethyl ketone peroxide mate '33" t W23 5 Stme 6 23 were added and the mixture was vigorously agitated to form we,re i s; 0 Sm fi the glycol in polyester-vinyl monomer emulsion. agmmng t e grams et y ene g Y were The emulsion was poured in a mold and hardened in 10 :dded. After further agitation, 0.5 cublc centimeter of minutes at room temperature.

imethylanihne and 9.5 gram of methyl ethyl ketone peroxide The resulting casting is hard, crackqesistam and dimem was added and the mixture was vigorously agitated to form the sionany stabh glycol in polyester-vinyl monomer emulsion.

The emulsion was poured in a mold and hardened in 10 EXAMPLES 5-13 minutes at room temperature. if f l d l d The resulting casting is hard, crack-resistant, and dimen- The glyco 'exten p0 yesters was to the stability of water-extended polyesters and the results are sionally stable. desc bed below rt A series of molds were made by hardening various glycol in EXAMPLE 3 ol ester emulsions and water in lyester emulsions. The

P y P 40 molds were then tested for weight losses at room temperature, A hardened unsaturated polyester resin matrix having a plu- F and at F for various periods of ma rahty of mersuces of glycol was formed m the follownllg Table 1 shows the results of this test, wherein resin A commanner.

rises 50 ercent st rene and 50 ercent of a 01 ester havin A reactor was charged with 100 grams of a polyester com- F compgsifion: y p p g position comprising 20 percent styrene, 0.01 percent methyl hydroquinone and 80 percent of a polyester having the follow- Moles ing composition: Maleic anhydride 8 Dimerized fatty acid formed by 2 Moles dimer izing 2 monobasic acids Phthalic anhydride 4 containing 18 carbon atoms Maleic anhydride 6 N (Empolll?l4)l l0 9 Propylene glycol 10.6 eopemy g yco To the polyester were added 3 grams of sorbitan sesquioleate. and Resm B (fompnses ff Styrene and 50 percent of a After agitating the mixture, 100 grams of propylene glycol Polyester havmg the composmon' were added. After further agitation, 0.5 cubic centimeter of dimethylaniline and 0.5 gram of benzoyl peroxide was added [so hthafic acid Mgles and the mixture was vigorously agitated to form the glycol in f anhydfide 4 polyester-vinyl monomer emulsion. Propylene glycol l 1.5

TABLE 1 Percent weight loss Time Room Percent t Percent Percent tested temper- Example Resin resin Glycol glycol water (days) ature F. F 22 Ethylene glycol. 2g 3 2 g 2 0 3 2g Glygerine 9g 8 5 2. 5 o ..r 9 .5 2.5 33 67 90 0 0 2 50 Propylene glycoL 5O JO 0 0 4 50 (ilyr-urinn. 50 ill) (I 0 l. 5 40 no no u n n 1.x m ll :13 m 07 1m 0 n 2. n umltml A no no 1m 5 3 x. z 20. r lunLl'ol n A m no no 7 2 10.1. 28.2

- been set forth hereinabove, it is not intended that the invention be limited solely thereto, but to include all the variations and modifications following within the scope of the appended claims.

We claim:

1. A hardened unsaturated polyester resin matrix having a plurality of interstices of a solution wherein glycol comprises at least about 80 percent by weight of the solution and the solution containing glycol is dispersed throughout the polyester resin phase as separate droplets and wherein the polyester resin comprises the copolymer of a. an unsaturated polyester, and

b. an ethylenically unsaturated monomer which is soluble in thepolyester and capable of forming an emulsion with glycol and thepolyester. v

2. The hardened matrixof claim 1 wherein the ethylenically unsaturated monomer is styrene.

' 3. The hardened matrix of claim 1 wherein the glycol is ethylene glycol.

' 4. The hardened matrix of claim 1 wherein the polyester resin comprises from about 40 percent to about 90 percent by weight of unsaturated polyester and from about 10 percent to about 60 percent by weight of ethylenically unsaturated monomer. I

5. The method of preparing a hardened glycol in polyester resin emulsion in which the polyester resin phase is hardened polyester resin phase is hardened by free-radical catalysis thus polymerizing the monomer.

6. The method of claim 5 wherein the emulsifier comprises from 0.1 percent to about 10 percent by weight of the mixture. 7. The method of claim 5 wherein the glycol is ethylene glycol.

8. The method ofi claim 5 wherein the polyester resin phase is hardened by adding to the emulsion a free-radical forming catalyst and heating the emulsion to activate the catalyst.

ll li t It 

2. The hardened matrix of claim 1 wherein the ethylenically unsaturated monomer is styrene.
 3. The hardened matrix of claim 1 wherein the glycol is ethylene glycol.
 4. The hardened matrix of claim 1 wherein the polyester resin comprises from about 40 percent to about 90 percent by weight of unsaturated polyester and from about 10 percent to about 60 percent by weight of ethylenically unsaturated monomer.
 5. The method of preparing a hardened glycol in polyester resin emulsion in which the polyester resin phase is hardened and the glycol phase remains as separate droplets dispersed throughout the polyester resin phase comprising adding a solution wherein glycol comprises at least about 80 percent by weight of the solution to a mixture of unsaturated polyester and an ethylenically unsaturated monomer which is soluble in the polyester and capable of forming an emulsion with glycol and the polyester and a predominantly lipophilic emulsifier and agitating the mixture to form an emulsion, and the polyester resin phase is hardened by free-radical catalysis thus polymerizing the monomer.
 6. The method of claim 5 wherein the emulsifier comprises from 0.1 percent to about 10 percent by weight of the mixture.
 7. The method of claim 5 wherein the glycol is ethylene glycol.
 8. The method of claim 5 wherein the polyester resin phase is hardened by adding to the emulsion a free-radical forming catalyst and heating the emulsion to activate the catalyst. 